A light emitting device uses a phenomenon in which light is emitted when forward current flows through a PN junction diode of a compound semiconductor, and mainly serves as a light source of a display device. Such a light emitting device does not require a filament, differently from an electric bulb, is resistant to vibration, and has a long lifespan and a fast response time.
Although an epi-layer is generally grown on a sapphire substrate, a technique for growing an epi-layer on a silicon substrate has been developed. However, as a nitride semiconductor layer (for example, a GaN layer) is grown on a silicon substrate, a lattice constant difference and a thermal expansion coefficient difference between the silicon substrate and the GaN layer is present and thus crystalline defects may occur.